The term “trigger point” was coined in 1942 by American Physician Dr Janet Travell to describe a clinical finding with the following characteristics:
- Pain related to a discrete, irritable point in skeletal muscle or fascia, not caused by acute local trauma, inflammation, degeneration, neoplasm, or infection.
- The painful point can be felt as a nodule or band in the muscle and a twitch response can be elicited on stimulation of the trigger point.
- Palpation of the trigger point reproduces the patient’s complaint of pain, and the pain radiates in a distribution typical of the specific muscle harboring the trigger point.
- The pain cannot be explained by findings on neurological examination.
Travell’s work treating US President John F. Kennedy’s back pain was so successful that she was asked to be the first female Personal Physician to the President.
Studies estimate that in 75–95 percent of cases, myofascial pain is a primary cause of regional pain. Myofascial pain is associated with muscle tenderness that arises from trigger points – focal points of tenderness, a few millimeters in diameter, found at multiple sites in a muscle and the fascia of muscle tissue. Biopsy tests found that trigger points are hyper irritable and electrically active muscle spindles in general muscle tissue
Trigger points may be caused by a number of factors, including acute or chronic muscle overload, activation by other trigger points, disease, psychological distress (via systemic inflammation), homeostatic imbalances, direct trauma to the region, accident trauma (such as a car accident which stresses many muscles and causes instant trigger points) radiculopathy, infections and health issues such as smoking.
Trigger points form only in muscles. They form as a local contraction in a small number of muscle fibers in a larger muscle or muscle bundle. These in turn can pull on tendons and ligaments associated with the muscle and can cause pain deep within a joint where there are no muscles.
Injections, including saline, local anesthetics such as procaine (Novocain), and anti inflammatory medications such as Traumeel, can provide almost immediate relief and can be effective when other methods fail. A low concentration, short acting local anesthetic such as procaine 0.5% without steroids or adrenaline is recommended. Dry needling methods such as acupuncture and intramuscular stimulation (IMS) can also be effective but causes more post-injection soreness.